This invention relates to extensible and retractable strut constructions, and more particularly to constructions of this type wherein telescoping members constitute the strut elements and are relatively axially movable between extended and retracted positions. The invention concerns improvements in U.S. Pat. No. 3,945,744 issued Mar. 23, 1976 to Joseph R. Metz and having the same assignee as the present invention.
In addition to the disclosure of this U.S. Pat. No. 3,945,744, in the past various types of extensible and retractable struts have been proposed and produced. These have variously employed manually operable, or automatic or semi-automatic locking or clamping devices by which the strut members were secured in various adjusted positions, and released from such positions, usually in response to manual activation of the clamping or locking device.
In some prior constructions the clamping operation required the tightening of a clamp screw, which was somewhat time consuming and not automatic. Other types of struts had locking or clamping devices of an automatic nature, but these were mostly uni-functional in their action, and operated in a particular manner which was predetermined by their construction and specific action. No option was had by the operator, as to whether or not the locking device could operate as the strut member attained the desired extended or retracted positions.
Additionally, many of the prior devices were not especially reliable, or else complicated in their manufacture in order to obtain the desired type of operation. This resulted in increased costs, particularly where special operations were needed to produce the various components. Sometimes the struts were accidentally or unintentionally released, causing inconvenience or damage, or both.